As of which year was the 4-wire, 240V circuit required for electrical installations?

The requirement for a 4-wire, 240V circuit was established as part of the National Electrical Code (NEC) updates, specifically in the 1996 edition. This update was primarily aimed at enhancing safety and compliance in electrical installations, particularly for residential applications. The 4-wire system includes two hot wires, one neutral, and one ground, allowing for a more efficient and safer distribution of power. It is particularly important for modern appliances that require 240V, providing better balance and reducing the risk of electrical shock.

This requirement was a response to the evolving understanding of electrical safety and the increased complexity of home appliances that necessitated a more robust and safer way to manage electrical loads. The implementation of this code has been fundamental in ensuring that electrical systems are more reliable, safer, and capable of handling the demands of modern living.